This invention relates generally to a tone hole covering for wind instruments having a novel backing disk with an outer collar capable of flexing to conform the pad's surface to the tone hole and provide an effective seal. The backing disk's flexibility allows the pad to conform to the tone hole's surface with minimal pressure even when not properly adjusted and reduces damage and wear caused by repeated contacts with the tone hole. Although generally applicable to all woodwind instruments, embodiments of the present invention are especially suited for use in flutes.
During this century, instrument tone hole coverings, also called pad assemblies or simply pads, have typically comprised a cardboard backed wool felt disk covered with Goldbeater's skin, wrapped around the cardboard and glued to its backside. The pad is fixed in a pad cup mounted over an instrument tone hole on a hinged mechanism so that the tone hole is sealed when the pad is in its closed position. Although such pads can initially be made to seal well, sensitivity to its environment and lack of dimensional stability of the felt and skin causes the pad surface to lose its integrity and allow air to leak at the interface between the pad and the tone hole.
U.S. Pat. No. 4,704,939 issued in 1987, disclosing a new pad that can maintain a flat sealing surface regardless of variations in temperature, moisture, or altitude. As a result of this design, pad life is extended and closure of the tone hole consistently requires only a light touch by the musician. To accomplish these advantages, the improved pad has a semi-rigid supporting unit for the felt. The pad's design allows its surfaces to be tilted to fit a tone hole with a perfectly planar surface through the leveling process of triangulation or, by a wedging action, to distort the planar surface to perfectly match a damaged or imperfect tone hole.
One embodiment of these improved pads is constructed by stretching a skin across a cushion ring fitted within a recess formed between inner and outer collars on the lower radial face of a rigid backing disk having a bendable lower margin. The skin is folded around the edge of the backing disk and secured to the disk's back side. The pad is secured to its cup with a retainer comprising a washer and a screw combination attached to a pad nut which is in turn attached to the bottom of a pad cup and centrally located within the cup's cavity. Upon tightening the retaining screw of the assembled unit, the flat washer forces the skin against the rigid inner collar. Other methods are also known for securing the pad assembly within the pad cup, including the usual friction held retainer utilized in French or open-hole pads.
Further improvements in pad design and methods of seating pad assemblies have been made which utilize a stabilizing disk locked in an adjusted position with an adhesive, to better support a flexible backing disk having inner and outer collars. As before, a cushion layer of uniform thickness is positioned between the inner and outer collars covered by the pad's sealing surface covered with a skin. Should the pad need further adjustment, the pad's surface can be made to coincide with the tone hole's surface by the usual wedging action of partial shims placed between the stabilizing and backing disks. U.S. Pat. No. 6,028,256 issued in 2000, and teaches that tension on the pad's skin can be reduced by providing the backing disk's outer collar with an upper curved lip formed by undercutting the backing disk's outer collar. The improved backing disk minimizes damages to a pad assembly's skin due to repeated contacts with a tone hole and environmental conditions.
Although pads manufactured according to these improved designs have performed well, rigorous leveling of pads is still required when initially installed on a flute and from time-to-time during the pad's lifetime. Because the leveling process is both time consuming and expensive a pad assembly is needed that is capable of conforming to the tone hole's surface without a rigorous leveling procedure and without sacrificing tone, touch, and other performance attributes important to the musician. The present invention addresses these needs.